1. Field of the Invention
The present invention relates to an electronic device including an element having a luminous material placed between electrodes and an electronic instrument using the electronic device as a display portion (indication display or indication monitor). Particularly, the present invention relates to an electronic device using a luminous material (hereinafter referred to as EL material) by which EL (Electro Luminescence) is obtained.
2. Description of the Related Art
In recent years, an electronic device (hereinafter referred to as EL display device) which uses a light-emitting device (hereinafter referred to as an EL element) using an EL phenomenon of a luminous material has been developed. Since the EL display device is a display device using the light-emitting device, a backlight as in liquid crystal display is not necessary, and further, since an angle of visibility is wide, the EL display device has attracted attention as a display portion of a portable equipment used outdoors.
There are two kinds of EL display devices, that is, a passive type (simple matrix type) and an active type (active matrix), and both types have been vigorously developed. Particularly, at present, the active matrix EL display device has attracted a great deal of attention. With respect to the EL material which becomes a luminescent layer emitting EL, there are an organic EL material and an inorganic EL material, and further, the organic EL material is classified into a low molecular (monomer) organic EL material and a high molecular (polymer) organic EL material. Especially, attention has been paid to the polymer organic EL material which is easier to handle and higher in heat resistance than the low molecular organic EL material. Incidentally, a luminous device using the organic EL material is called OLED (Organic Light Emitting Diodes) in Europe.
The active matrix EL display device is characterized in that an electric field effect transistor (hereinafter referred to as FET) is provided in each of pixels constituting a pixel portion, and an amount of electric current made to flow through an EL element is controlled by the FET. However, there has been a problem in that when electrical characteristics of the FETs vary among pixels, luminous characteristics of the EL elements provided in the respective pixels also vary.